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Presentation of integrins on leukocyte microvilli: a role for the extracellular domain in determining membrane localization.

Abitorabi MA, Pachynski RK, Ferrando RE, Tidswell M, Erle DJ - J. Cell Biol. (1997)

Bottom Line: Therefore, differences between the transmembrane and cytoplasmic domains of alpha4 and beta2 integrins do not account for differences in ability to support attachment under flow or in membrane localization.Integrins alpha4beta1, alpha5beta1, alpha6Abeta1, alphavbeta3, and alphaEbeta7 also localized to microvilli.Transmembrane proteins known or suspected to associate with extracellular domains of microvillous integrins, including tetraspans and CD47, were concentrated on microvilli as well.

View Article: PubMed Central - PubMed

Affiliation: The Lung Biology Center, Department of Medicine, University of California, San Francisco, California 94143, USA.

ABSTRACT
Adhesion of blood leukocytes to the endothelium involves multiple steps including initial attachment (tethering), rolling, and firm arrest. Presentation of adhesion molecules on leukocyte microvilli can substantially enhance tethering. Localization of L-selectin to microvilli and of CD44 to the planar cell body have been shown to depend upon their transmembrane and cytoplasmic domains. We investigated the role of leukocyte integrin transmembrane and cytoplasmic domains in initiating adhesion under flow and in microvillous localization. Integrins alpha4beta7, alphaLbeta2, and alphaMbeta2 were heterologously expressed in K562 cells. alpha4beta7 initiated adhesion under flow and localized to microvilli, whereas beta2 integrins did not initiate adhesion and localized to the cell body. Chimeric integrins were produced by replacing the alpha4beta7 cytoplasmic and/or transmembrane domains with the homologous domains of alphaLbeta2 or alphaMbeta2. Unexpectedly, these chimeras efficiently mediated adhesion to the alpha4beta7 ligand mucosal addressin cell adhesion molecule-1 under flow and localized to microvilli. Therefore, differences between the transmembrane and cytoplasmic domains of alpha4 and beta2 integrins do not account for differences in ability to support attachment under flow or in membrane localization. Integrins alpha4beta1, alpha5beta1, alpha6Abeta1, alphavbeta3, and alphaEbeta7 also localized to microvilli. Transmembrane proteins known or suspected to associate with extracellular domains of microvillous integrins, including tetraspans and CD47, were concentrated on microvilli as well. These findings suggest that interactions between the extracellular domains of integrins and associated proteins could direct the assembly of multimolecular complexes on leukocyte microvilli.

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Static adhesion of  transfectants to immobilized  ligands. Adhesion of various  integrin transfectants to  MAdCAM-1 (top) and ICAM-1  (bottom) was measured in  the presence and absence of  Mn2+. Bars indicate SEM.  nd, not determined.
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Figure 3: Static adhesion of transfectants to immobilized ligands. Adhesion of various integrin transfectants to MAdCAM-1 (top) and ICAM-1 (bottom) was measured in the presence and absence of Mn2+. Bars indicate SEM. nd, not determined.

Mentions: We analyzed the ability of integrin-transfected K562 cells to adhere to MAdCAM-1, an α4β7 ligand, and ICAM-1, an αLβ2 ligand, under static (no flow) conditions (Fig. 3). After transfection with α4 cDNA alone, K562 cells express α4β1 but not α4β7 (Tidswell et al., 1997). These cells failed to adhere to MAdCAM-1. In contrast, cells transfected with both α4 and β7 (K562-α4β7) adhered efficiently to MAdCAM-1. As previously reported, adhesion was increased in the presence of Mn2+. The chimeric transfectants, K562-α4β7(αLβ2c) and K562-α4β7(αMβ2tc), also adhered to MAdCAM-1, and the extent of adhesion was very similar for chimeric and wild-type α4β7 transfectants. As expected, K562-α4β7 cells did not adhere to ICAM-1, whereas K562-αLβ2 cells did.


Presentation of integrins on leukocyte microvilli: a role for the extracellular domain in determining membrane localization.

Abitorabi MA, Pachynski RK, Ferrando RE, Tidswell M, Erle DJ - J. Cell Biol. (1997)

Static adhesion of  transfectants to immobilized  ligands. Adhesion of various  integrin transfectants to  MAdCAM-1 (top) and ICAM-1  (bottom) was measured in  the presence and absence of  Mn2+. Bars indicate SEM.  nd, not determined.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139798&req=5

Figure 3: Static adhesion of transfectants to immobilized ligands. Adhesion of various integrin transfectants to MAdCAM-1 (top) and ICAM-1 (bottom) was measured in the presence and absence of Mn2+. Bars indicate SEM. nd, not determined.
Mentions: We analyzed the ability of integrin-transfected K562 cells to adhere to MAdCAM-1, an α4β7 ligand, and ICAM-1, an αLβ2 ligand, under static (no flow) conditions (Fig. 3). After transfection with α4 cDNA alone, K562 cells express α4β1 but not α4β7 (Tidswell et al., 1997). These cells failed to adhere to MAdCAM-1. In contrast, cells transfected with both α4 and β7 (K562-α4β7) adhered efficiently to MAdCAM-1. As previously reported, adhesion was increased in the presence of Mn2+. The chimeric transfectants, K562-α4β7(αLβ2c) and K562-α4β7(αMβ2tc), also adhered to MAdCAM-1, and the extent of adhesion was very similar for chimeric and wild-type α4β7 transfectants. As expected, K562-α4β7 cells did not adhere to ICAM-1, whereas K562-αLβ2 cells did.

Bottom Line: Therefore, differences between the transmembrane and cytoplasmic domains of alpha4 and beta2 integrins do not account for differences in ability to support attachment under flow or in membrane localization.Integrins alpha4beta1, alpha5beta1, alpha6Abeta1, alphavbeta3, and alphaEbeta7 also localized to microvilli.Transmembrane proteins known or suspected to associate with extracellular domains of microvillous integrins, including tetraspans and CD47, were concentrated on microvilli as well.

View Article: PubMed Central - PubMed

Affiliation: The Lung Biology Center, Department of Medicine, University of California, San Francisco, California 94143, USA.

ABSTRACT
Adhesion of blood leukocytes to the endothelium involves multiple steps including initial attachment (tethering), rolling, and firm arrest. Presentation of adhesion molecules on leukocyte microvilli can substantially enhance tethering. Localization of L-selectin to microvilli and of CD44 to the planar cell body have been shown to depend upon their transmembrane and cytoplasmic domains. We investigated the role of leukocyte integrin transmembrane and cytoplasmic domains in initiating adhesion under flow and in microvillous localization. Integrins alpha4beta7, alphaLbeta2, and alphaMbeta2 were heterologously expressed in K562 cells. alpha4beta7 initiated adhesion under flow and localized to microvilli, whereas beta2 integrins did not initiate adhesion and localized to the cell body. Chimeric integrins were produced by replacing the alpha4beta7 cytoplasmic and/or transmembrane domains with the homologous domains of alphaLbeta2 or alphaMbeta2. Unexpectedly, these chimeras efficiently mediated adhesion to the alpha4beta7 ligand mucosal addressin cell adhesion molecule-1 under flow and localized to microvilli. Therefore, differences between the transmembrane and cytoplasmic domains of alpha4 and beta2 integrins do not account for differences in ability to support attachment under flow or in membrane localization. Integrins alpha4beta1, alpha5beta1, alpha6Abeta1, alphavbeta3, and alphaEbeta7 also localized to microvilli. Transmembrane proteins known or suspected to associate with extracellular domains of microvillous integrins, including tetraspans and CD47, were concentrated on microvilli as well. These findings suggest that interactions between the extracellular domains of integrins and associated proteins could direct the assembly of multimolecular complexes on leukocyte microvilli.

Show MeSH
Related in: MedlinePlus